A conveyor such as an escalator or moving walkway has a plurality of steps that are provided with step rollers and is arranged such that these steps are driven by a chain drive mechanism to perform circulatory movement between a passenger entrance and passenger exit whilst supported and guided by a step guide rail.
In the case of a moving walkway, typically a plurality of steps move in the horizontal direction. These steps are sometimes specifically referred to as “foot boards”, but, in the present specification, will be referred to by the general term of “steps” in the case of a moving walkway also.
Typically, the chain drive mechanism is of a type in which the returning extremity of a step chain that links in endless fashion step rollers with a prescribed pitch (link length r) is wound onto a driving sprocket wheel (sometimes called master driving sprocket wheel) that is rotated by receiving drive force from a drive motor, the drive force of the motor being thus transmitted to the step chain. This chain drive mechanism is usually arranged within a structure called a truss in the center of the passenger entrance or in the vicinity of the passenger exit of the conveyor.
While it was conventionally considered that ample space was necessary for installation of the truss in which the chain drive mechanism is arranged, in recent years, reduction of the size of the truss is being called for and attempts are being made to save space by reducing the overall thickness of the conveyor.
If, in conformity with the reduction in size of the truss, a sprocket wheel of small diameter is employed for the driving sprocket wheel, comparatively large speed irregularities are generated in the step rollers that are linked with the step chain; these speed irregularities appear as vibration of the steps, adversely affecting the comfort of passengers on the conveyor.
The present applicants therefore first proposed a conveyor of a construction such as would enable generation of speed irregularity in the step rollers to be reduced. An example of such a construction is Laid-open Japanese Patent Publication (Tokkai 2003-252560).
FIG. 1 to FIG. 3 are layout diagrams of a prior art conveyor. The conveyor 1 is a moving walkway arranged practically horizontally with respect to a road surface and provided with a step guide rail 3 that makes a circuit between a passenger entrance 1a and passenger exit 1b in the interior of a structure 2 called a truss. This step guide rail 3 is constituted so as to guide the movement of a plurality of steps 4.
The plurality of steps 4 are provided with respective step rollers 5, these step rollers 5 being moved along the step guide rail 3.
The step guide rail 3 includes a main rail body 3a having a supporting face on its outgoing path side and a restraining rail 3b provided on its return side. As the steps 4 move along the outgoing path side the steps 4 move in the direction of the arrow A from the passenger entrance 1a towards the passage exit 1b. A rubber plate 6 is provided in the vicinity of the passenger entrance 1a and passenger exit 1b. The steps 4 move in the downward direction of this rubber plate 6.
As the steps 4 move along the return side the step rollers 5 move between the main rail body 3a and the restraining rail 3b from the passenger entrance 1b towards the passenger exit 1a. Also, at the side of the passenger entrance 1a, a moveable rail 3c is provided that is capable of movement in a direction such as to separate from this main rail body 3a. 
Since the step rollers 5 of the steps 4 that are mutually linked with a prescribed pitch (link length r) are driven in a condition in abutment with the step guide rail 3, the steps 4 are guided by the step guide rail 3 and can move without a gap continuously between the passenger entrance 1a and passenger exit 1b. 
Since the returning portion of the step chain 7 is wound onto the driving sprocket wheel 9 that is rotated by receiving drive force from the drive motor 8, the chain drive mechanism transmits the drive force of the drive motor 8 to the step chain 7 through the drive chain 10 and the driving sprocket wheel 9.
Specifically, the drive chain 10 and drive motor 8 constitute a rotary drive device. The driving sprocket wheel 9, having received drive force from this rotary drive device, is operated to feed the step chain 7 and the step rollers 5 linked therewith in a condition meshed with the step rollers 5 that are linked by the step chain 7 between one and another adjacent tooth.
A driven sprocket wheel (sometimes called slave sprocket wheel) 11 of practically the same diameter as the driving sprocket wheel (sometimes called master sprocket wheel) 9 and that rotates driven by the driving sprocket wheel 9 is provided at the side of the passenger entrance 1a of the conveyor 1. The step chain 7 is passed over this driven sprocket wheel 11 and driving sprocket wheel 9 from the driven sprocket wheel 11 to the driving sprocket wheel 9.
The driven sprocket wheel 11 is biased in a direction such as to separate from the driving sprocket wheel 9, by means of a spring member 12 of a chain tensioning mechanism so as to tension the step chain 7 in the horizontal direction to prevent slackness in the direction of feed. A moveable rail 3c of the step guide rail 3 is also moved in a direction such as to separate from the driving sprocket wheel 9, in a manner that is linked with the driven sprocket wheel 11.
The step rollers 5 mesh with the driving sprocket wheel 9 in the process of changing over from linear motion in the horizontal direction following the step guide rail 3 to curvilinear motion that executes rotation with the diameter of the driving sprocket wheel 9. This gives rise to irregularities in the speed of movement.
This speed irregularity that is generated in the step rollers 8 gives rise to vibration in the steps 4, which adversely affects passenger comfort of the passengers on the conveyor 1. A hill-shaped curved section 13 that absorbs such speed irregularity of the step rollers 5 is therefore provided in the vicinity of the driving sprocket wheel 9 on the outgoing path side of the main rail body 3a, in the vicinity of the driving sprocket wheel 9 of the restraining rail 3b that is provided on the return side of the step guide rail 3 and in the vicinity of the driven sprocket wheel 11 on the outgoing path side and return side of the moveable rail 3c. 
The step rollers 5 pass along a track corresponding to the shape of these hill-shaped bent sections 13. Recesses 14 are respectively provided in positions facing the bent sections 13 so as to enable movement of the step rollers 5 along these bent sections 13.
Furthermore, a restraining member 15 that abuts the upper edge of the step rollers 5 is provided in a position facing the step guide rail 3, in order to prevent occurrence of riding up of the next step roller 5, due to the effect of the preceding step roller 5 passing over the bent section 13, at a position facing a location upstream of the bent section 13 provided in the vicinity of the driving sprocket wheel 9 on the side of the outgoing path of the main rail body 3a. 
Such a restraining member 15 is likewise provided in a position facing a position downstream of the bent section 13 that is provided in a position in the vicinity of the driven sprocket wheel 11 on the side of the outgoing path of the moveable rail 3c. 
Speed irregularity i.e. vibration that is generated in the steps 4 can thus be suppressed by making the movement of the step rollers 5 smooth, even in the case of reverse drive of the conveyor 1, by providing a bent section 13 in a location in the vicinity of the driving sprocket wheel 9 of the restraining rail 3b provided on the return side of the step guide rail 3.
It should be noted that even if the shape of the bent section 13 is valley-shaped rather than hill-shaped, speed irregularities of the step rollers 5 can be absorbed in the same way.
In a conveyor as described above, consideration may be given to interposing resilient members having flexibility made of for example rubber on the outside around the rotary shaft of the step rollers 5, in order to prevent generation of noise during the rotation of the step rollers 5.
The tensile force of a chain tensioning mechanism such as the spring member 12 acts so as to effect advancement in the horizontal direction in the straight-line section on the step rollers 5 on the step guide rail 3, so a large pressing force pressing these hill-shaped bent sections 13 onto the step rollers 5 acts when the step rollers 5 attempt to cross the hill-shaped bent section 13 formed on the step guide rail 3.
If a resilient member is interposed around the shaft of the step roller 5, the pressing force that is exerted when the step roller passes this bent section 13 acts in the radial direction of the step roller 5, compressing the resilient member. There is therefore a risk that the track of the movement of the shafts of the step rollers, following the shape of the bent section 13, may depart from the track that was set beforehand with a view to suppressing speed irregularity, with the result that the desired diminution of speed irregularity may not be obtained.
The same applies when the bent section 13 formed on the step guide rail 3 is valley-shaped. When the bent section is valley-shaped, pressing force is applied in the same way between this bent section and the restraining members of projecting shape projecting downwards that are arranged facing this bent section so as to enable the step rollers 5 to follow a predetermined track along the shape of the valley-shaped bent section 13. Thus the resilient member of the step rollers 5 is compressed in the radial direction, with the risk that speed irregularities may not be adequately suppressed.
Also, although, in a prior art conveyor, a restraining member 15 was provided in a position facing the step guide rail 3 in order to prevent the step rollers located to the downstream (i.e. on the side nearest the passenger entrance 1a) of the hill-shaped bent section 13 from riding upwards, as the step rollers 5 are thus gripped from above and below by the restraining member 15 and the step guide rail 3, causing the step rollers 5 to move in sliding fashion rather than rotating, there was a risk that the resulting sliding friction would damage not just the step rollers 5 themselves but rather both the restraining member 15 and the step rollers 5.
If, on the other hand, in order to prevent such sliding, a gap was provided between the restraining member 15 and the step rollers 5, this resulted in the movement of the step rollers 5 being displaced in position towards the restraining member 15 by the amount of this gap, with the risk that speed irregularities would thereby be increased.
Also, in the prior art conveyor, if the step chain upstream and downstream of the step roller 5 extends in a straight line at the connecting section with the hill-shaped or valley-shaped bent section 13, some degree of bending must take place at this connecting section in order for the subsequent step roller 5 to be able to track the change of speed when the step roller 5 passes the connecting section to the hill-shaped or valley-shaped bent section 13 and this gives rise to a risk of generation of dynamic shock vibration when the step rollers 5 pass this point.
Accordingly, a first object of the present invention is to provide a conveyor wherein generation of speed irregularities in the steps can be adequately suppressed even if a resilient member is interposed around the shaft of the step rollers and the diameter thereof is compressed by pressing force.
Also, an object is to provide a conveyor wherein generation of speed irregularities between step roller and step can be adequately suppressed while suppressing damage to the step rollers etc by avoiding gripping of the running step rollers from above and below.
Also, a second object of the present invention is to provide a conveyor wherein generation of speed irregularities between the step roller and the step can be adequately suppressed without generating dynamic shock vibration during passage of the step rollers over the connecting section to the hill-shaped or valley-shaped bent section.